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WORM_SILLY.WXXZ

December 15, 2016
 Analysis by: Michael Jay Villanueva
 ALIASES:

Worm.Win32.Foler.a (Tencent); Worm:Win32/Foler.C (Microsoft)

 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


This worm arrives via removable drives. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

  TECHNICAL DETAILS

File Size:

474,112 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

14 Dec 2016

Arrival Details

This worm arrives via removable drives.

It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This worm drops the following copies of itself into the affected system and executes them:

  • %User Profile%\MyHood\{Malware Name}.exe

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

It drops the following component file(s):

  • {Removable Drive Letter}:\{Folder Name available on the drive}.exe -> detected as WORM_SILLY.WXXZLDR
    This serves as the loader of the dropped malware copy on the removable drive, wherein it contains the name of each folder found on the drive to reinfect a machine.
    If no folder was found on the drive, the malware will create a folder "{Removable Drive Letter}:\Data", in order to use it as the dropped loader's name, ie. {Removable Drive Letter}:\Data.exe

It creates the following folders:

  • %User Profile%\MyHood

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

Autostart Technique

This worm drops the following file(s) in the Windows User Startup folder to enable its automatic execution at every system startup:

  • %User Startup%\ccnfg.lnk -> Shortcut file to the malware's dropped copy

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Documents and Settings\{user}\Start Menu\Programs\Startup on Windows 2000 and XP, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows Vista, 7, and 8.)

Propagation

This worm drops the following copies of itself in all physical and removable drives:

  • {Removable Drive Letter}:\{Malware Name}.exe

Other Details

This worm does the following:

  • It hides all the folders found on removable drives in order to trick the user on clicking the dropped loader of the malware.

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

12.960.04

FIRST VSAPI PATTERN DATE:

14 Dec 2016

VSAPI OPR PATTERN File:

12.961.00

VSAPI OPR PATTERN Date:

15 Dec 2016

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 3

Remove malware/grayware files dropped/downloaded by WORM_SILLY.WXXZ. (Note: Please skip this step if the threats listed below have already been removed.)

    Step 4

    Search and delete files detected as WORM_SILLY.WXXZ

    [ Learn More ]
    Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.

    Step 5

    Search and delete these folders

    [ Learn More ]
    Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
    • %User Profile%\MyHood

    Step 6

    Search and delete these files

    [ Learn More ]
    There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
    • {Removable Drive Letter}:\{Folder Name available on the drive}.exe
    • {Removable Drive Letter}:\{Malware Name}.exe
    • {Removable Drive Letter}:\Data.exe
    • %User Startup%\ccnfg.lnk

    Step 7

    Scan your computer with your Trend Micro product to delete files detected as WORM_SILLY.WXXZ. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.


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